ok..Previously we had done PXE boot of ESXi5.1.for this out setup is like this..
=>Virtual m/c Windows 2008 R2 having DHCP setup
=>tftp server on ubuntu 11.10.also in /var/lib/tftpboot/ESX we had mounted ESX.iso again in ESX/ks.cfg file was kickstart file for ESX5.1
=>When we create new VM and try to power on it ;On Console we need to write name of OS we need to network boot.after that all the booting does get started automatically.
Now upto this whatever we had done we need to automate this using powershell and powerCLI commands .No need to automate DHCP nd TFTP setup.By using that PXE server which is in our case ubuntu 11.10 we need to install ESX5.1 on bare metal.